A photographic system comprising reacting an aromatic primary amine developing agent, which has been oxidized with exposed silver halide acting as an oxidizing agent, and a coupler to form an indophenol, indaniline, indamine, azomethine, phenoxazine, phenazine or the like dye to produce a color image is well known. In such a photographic system, a subtractive color producing process is employed in which a color image is formed of yellow, magenta and cyan dyes.
Hitherto, phenols or naphthols have been employed as cyan couplers. However, cyan dyes formed from such couplers have unsatisfactory spectral absorption characteristics, heat resistance, moisture resistance and light resistance. Various couplers with improved properties have heretofore been developed.
For instance, U.S. Pat. No. 4,728,598 discloses novel couplers, but the dyes produced therefrom have a broad color hue range in which the maximum absorption peak wavelength falls between 538 nm and 602 nm. The disclosed novel couplers are therefore not practical. In addition, it has also been found that the images obtained from the couplers have an extremely poor color fastness.
The present inventors have earnestly studied imidazo[1,2-b]pyrazoles and have surprisingly found that introduction of a perfluoroalkyl group into the 2-position of the compounds provides cyan couplers with excellent properties.